Decoupling fault diagnosis method for two-degree-of-freedom switched reluctance motor

Abstract

The invention discloses a decoupling fault diagnosis method for a two-degree-of-freedom switched reluctance motor, and the method comprises the steps: calculating the predicted current of each phase winding of a rotary motion unit and a linear motion unit of the two-degree-of-freedom switched reluctance motor; the actual switching state of each phase bridge arm switching tube of the power converter is obtained by combining the predicted current of each phase winding, the reference current and the evaluation function, and the equivalent switching state of each phase bridge arm switching tube of the power converter is obtained according to the predicted current and the actual current of each phase winding; and comparing the actual switching state with the equivalent switching state to realize fault diagnosis and positioning of the two-degree-of-freedom switched reluctance motor power converter. The method provided by the invention can effectively diagnose the short circuit and open circuit faults of the power triodes of the rotary motion unit and the linear motion unit of the two-degree-of-freedom switched reluctance motor only by controlling the intermediate variable, does not need to change the modular structure of the power converter, and has good engineering value and application prospect.

Description

Technical Field

[0001] The present invention relates to the field of decoupling fault diagnosis of a two-degree-of-freedom switched reluctance motor, and in particular to a fault diagnosis scheme for a power converter in a rotary motion unit and a linear motion unit of a two-degree-of-freedom switched reluctance motor based on actual switching states and equivalent switching states. Background Art

[0002] The two-degree-of-freedom switched reluctance motor has the advantages of high reliability, strong fault tolerance and high adaptability. It is widely used in fields with high reliability requirements such as automation control, electric vehicles, and aerospace. The drive system of the rotary motion unit and the linear motion unit of the two-degree-of-freedom switched reluctance motor is the weakest part. The power transistor is the core component of the power converter and is also the most easily damaged component. When the motor runs for a long time, the power transistor will short-circuit and open-circuit faults, causing safety hazards. The traditional two-degree-of-freedom switched reluctance motor fault diagnosis method increases the number of sensors, changes the power converter structure, or uses complex algorithms to identify and locate the power transistor fault, which not only increases the system cost, destroys the modular design structure of the power converter, and increases the calculation complexity of the algorithm, but also the currents at multiple positions are coupled together, and it is impossible to independently diagnose the faults of each bridge arm and each motion unit. Therefore, in order to avoid the influence of the fault diagnosis of the power converter of the rotary motion unit and the linear motion unit of the two-degree-of-freedom switched reluctance motor, and to achieve the independence and accuracy of the fault diagnosis of the two-degree-of-freedom switched reluctance motor, it is urgent to propose an effective decoupling fault diagnosis scheme. Summary of the invention

[0003] The purpose of the present invention is to provide a two-degree-of-freedom switched reluctance motor decoupling fault diagnosis method in view of the problems existing in the prior art.

[0004] The technical solution proposed by the present invention is:

[0005] A decoupling fault diagnosis method for a two-degree-of-freedom switched reluctance motor is characterized by: based on the current of each phase winding of the rotary motion unit and the linear motion unit of the two-degree-of-freedom switched reluctance motor, the predicted current of each phase winding is calculated; the actual switching state of the bridge arm switch tube of each phase of the power converter is obtained by combining the predicted current, the reference current and the evaluation function; the equivalent switching state of the bridge arm switch tube of each phase of the power converter is obtained according to the predicted current and the actual current of the winding of each phase; finally, by comparing the actual switching state and the equivalent switching state, a fast and accurate fault diagnosis of the transistor of the power converter of the two-degree-of-freedom switched reluctance motor is achieved.

[0006] A two-degree-of-freedom switched reluctance motor decoupling fault diagnosis method of the present invention comprises the following steps:

[0007] Step 1: Calculate the predicted current value of each phase winding under different states at the (k+1)th sampling moment;

[0008] Step 2: Obtain the actual switching state D of the switch tube of each phase bridge arm of the power converter according to the predicted current value of each phase winding, the reference current and the evaluation function;

[0009] Step 3: Obtain the equivalent switch state D of each phase arm switch of the power converter according to the predicted current value and the actual current value of each phase winding at the (k+1)th sampling moment * ;

[0010] Step 4: Compare the actual switching state D of each phase arm switch of the power converter with the equivalent switching state D * Perform fault diagnosis on power transistors of power converters;

[0011]

[0012] The predicted current value at the moment is:

[0013]

[0014] Where k is the sampling point number; i(k) is the actual current value at the kth sampling moment; i(k+1) is the predicted current value at the (k+1)th sampling moment; ψ(k) is the flux linkage value at the kth sampling moment; U(k) is the phase voltage at the kth sampling moment; θ(k) is the rotor position angle at the kth sampling moment; ω(k) is the angular velocity at the kth sampling moment; R is the winding internal resistance; T s is the sampling period.

[0015] The two-degree-of-freedom switched reluctance motor power converter adopts an asymmetric half-bridge structure. When the upper and lower power transistors are both turned on, an excitation circuit ST1 is formed. The predicted current is i up ; When the upper power transistor is turned off and the lower power transistor is turned on, the lower freewheeling loop ST2 is formed, and the predicted current is i free When the upper power transistor is turned on and the lower power transistor is turned off, the upper freewheeling loop ST3 is formed, and the predicted current is i free ; When both the upper and lower power transistors are turned off, a demagnetization circuit ST4 is formed, and the predicted current is i down .

[0016] Furthermore, the expression of the evaluation function is:

[0017] J=[i ref -i pre (k+1)](2)

[0018] In the formula, i ref is the reference current; i pre(k+1) is the predicted current value at the (k+1)th sampling moment. The actual switching state D of the bridge arm switch tube of each phase of the power converter is obtained according to the predicted current of each phase winding, the reference current and the evaluation function. The actual switching state D is 1, 0, and -1 respectively, and the predicted phase current is i up 、i free 、i down .

[0019] When the actual current i(k+1) is equal to the predicted current i up When they are equal, the equivalent switch state D * is 1; when the actual current i(k+1) is equal to the predicted current i free When they are equal, the equivalent switch state D * is 0; when the actual current i(k+1) is equal to the predicted current i down When they are equal, the equivalent switch state D * is -1.

[0020] Furthermore, by comparing the actual switch state D with the equivalent switch state D * Identify and locate short-circuit and open-circuit faults of power transistors.

[0021] When the actual switch state D is equal to the equivalent switch state D * If they are the same, the power transistor is in normal state.

[0022] When the actual switch state D is 1, the equivalent switch state D * When it is 0, a shutdown pulse signal is injected into the upper power transistor; at the next sampling moment, when the actual current i(k+2) and the predicted current i free When the actual current i(k+2) is equal to the predicted current i down When they are equal, the lower power transistor has an open circuit fault.

[0023] When the actual switch state D is -1, the equivalent switch state D * When it is 0, a conduction pulse signal is injected into the upper power transistor; at the next sampling moment, when the actual current i(k+2) and the predicted current i free When the actual current i(k+2) is equal to the predicted current i up When they are equal, the lower power transistor has a short circuit fault.

[0024] When the actual switch state D is 0, the equivalent switch state D * When it is -1, the lower power transistor has an open circuit fault; when the actual switch state D is 0, the equivalent switch state D * When it is 1, the upper power transistor has a short circuit fault.

[0025] When the actual switch state D is 1, the equivalent switch state D * When the actual switch state D is -1, the upper and lower power transistors both have open circuit faults; when the actual switch state D is -1, the equivalent switch state D * When it is 1, both the upper and lower power transistors have short circuit faults.

[0026] Beneficial effect: Due to the adoption of the above technical solution, the present invention is applicable to a two-degree-of-freedom switched reluctance motor decoupling fault diagnosis method, which realizes fault diagnosis only by means of intermediate variables in the control algorithm, thus maintaining the modular structure of the power converter and not introducing additional complex fault diagnosis algorithms. The two-degree-of-freedom switched reluctance motor decoupling fault diagnosis method utilizes the intermediate variables of each phase winding, and each phase bridge arm and each motion unit are relatively independent and do not interfere with each other during diagnosis, thereby realizing the decoupling fault diagnosis and positioning of the power converter in the rotary motion unit and the linear motion unit of the two-degree-of-freedom switched reluctance motor. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 The present invention is a flow chart of a decoupling fault diagnosis method for a two-degree-of-freedom switched reluctance motor.

[0028] Figure 2 It is a current path diagram of the excitation circuit of the two-degree-of-freedom switched reluctance motor power converter of the present invention.

[0029] Figure 3 It is a current path diagram of the freewheeling loop of the two-degree-of-freedom switched reluctance motor power converter of the present invention.

[0030] Figure 4 The present invention discloses a current path diagram of a freewheeling loop on a two-degree-of-freedom switched reluctance motor power converter.

[0031] Figure 5 It is a current path diagram of the demagnetization circuit of the two-degree-of-freedom switched reluctance motor power converter of the present invention. DETAILED DESCRIPTION

[0032] An embodiment of a three-phase 12 / 8 two-degree-of-freedom switched reluctance motor applicable to the present invention is further described below in conjunction with the accompanying drawings:

[0033] Figure 1 It is a flow chart of the decoupling fault diagnosis method of a two-degree-of-freedom switched reluctance motor, where i(k+1) and i(k+2) are the actual currents at the (k+1) and (k+2) sampling moments, respectively. up 、i free 、i down are the predicted currents in the excitation circuit, freewheeling circuit, and demagnetization circuit, respectively. D is the actual switch state, and D * It is the equivalent switch state.

[0034] The voltage equation of a two-degree-of-freedom switched reluctance motor is:

[0035]

[0036] Where U is the phase voltage; i is the phase current; ψ is the phase flux; R is the winding internal resistance; θ is the rotor position angle; ω is the angular velocity.

[0037] The predicted current value at the next moment is:

[0038]

[0039] Where k is the sampling point number; i(k) is the actual current value at the kth sampling moment; i(k+1) is the current prediction value at the (k+1)th sampling moment; U(k) is the phase voltage at the kth sampling moment; θ(k) is the rotor position angle at the kth sampling moment; ω(k) is the angular velocity at the kth sampling moment; R is the winding internal resistance; T s is the sampling period.

[0040] Figure 2 It is the current path diagram of the two-degree-of-freedom switched reluctance motor power converter, where A is the A-phase winding of the two-degree-of-freedom switched reluctance motor, S1 and S2 are the power transistors of the A-phase bridge arm, and D1 and D2 are the freewheeling diodes of the A-phase bridge arm. The current of the two-degree-of-freedom switched reluctance motor power converter has three circuits, namely the excitation circuit, the freewheeling circuit, and the demagnetization circuit. The power transistors in each current circuit have corresponding switching states, and the freewheeling circuit corresponds to two switching states. According to the predicted current formula, there are corresponding predicted current values ​​in different current circuits. Figure 2 When the medium power transistors S1 and S2 are both turned on, they form an excitation circuit ST1, and the predicted current is i up ; Figure 3 When the medium power transistor S1 is turned off and the power transistor S2 is turned on, the lower freewheeling loop ST2 is formed, and the predicted current is i free ; Figure 4 When the medium power transistor S1 is turned on and the power transistor S2 is turned off, the upper freewheeling loop ST3 is formed, and the predicted current is i free ; Figure 5 When the medium power transistors S1 and S2 are both turned off, they form a demagnetization circuit ST4, and the predicted current is i down .

[0041] The expression of the evaluation function is:

[0042] J=[i ref -i pre (k+1)](3)

[0043] In the formula, i ref is the reference current; ipre (k+1) is the predicted current value at the (k+1)th sampling moment. The actual switch state D of each phase bridge arm switch tube of the power converter is obtained based on the predicted current of each phase winding, the reference current and the evaluation function. The actual switch state D is 1, 0, and -1 respectively, and the predicted phase current is i up 、i free 、i down .

[0044] When the actual current i(k+1) is equal to the predicted current i up When they are equal, the equivalent switch state D * is 1; when the actual current i(k+1) is equal to the predicted current i free If they are equal, then the equivalent switch state D * is 0; when the actual current i(k+1) is equal to the predicted current i down If they are equal, then the equivalent switch state D * is -1.

[0045] By comparing the actual switch state D and the equivalent switch state D * Identify and diagnose short-circuit and open-circuit faults of power transistors.

[0046] When the actual switch state D is 1, the equivalent switch state D * When it is 0, a shutdown pulse signal is injected into the upper power transistor S1; if at the next sampling moment, when the actual current i(k+2) and the predicted current i free When the actual current i(k+2) is equal to the predicted current i down When they are equal, it indicates that the lower power transistor S2 has an open circuit fault.

[0047] When the actual switch state D is -1, the equivalent switch state D * When it is 0, a conduction pulse signal is injected into the upper power transistor S1; if at the next sampling moment, when the actual current i(k+2) and the predicted current i free When the actual current i(k+2) is equal to the predicted current i up When they are equal, it indicates that the lower power transistor S2 has a short circuit fault.

[0048] When the actual switch state D is 0, the equivalent switch state D * When it is -1, it indicates that the lower power transistor S2 has an open circuit fault; when the actual switch state D is 0, the equivalent switch state D * When it is 1, it indicates that the upper power transistor S1 has a short circuit fault.

[0049] When the actual switch state D is 1, the equivalent switch state D *When the actual switch state D is -1, the upper power transistor S1 and the lower power transistor S2 both have open circuit faults; when the actual switch state D is -1, the equivalent switch state D * When it is 1, both the upper power transistor S1 and the lower power transistor S2 have short circuit faults.

[0050] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes according to the technical scheme and inventive concept of the present invention within the technical scope disclosed by the present invention, which should fall within the protection scope of the technical scheme of the present invention.

Claims

1. A two-degree-of-freedom switched reluctance motor decoupling fault diagnosis method, characterized in that: Based on the currents of each phase winding of the rotary motion unit and the linear motion unit of the two-degree-of-freedom switched reluctance motor, the predicted current of each phase winding is calculated; the actual switching state of the switch tube of each phase bridge arm of the power converter is obtained by combining the predicted current, the reference current and the evaluation function; the equivalent switching state of the switch tube of each phase bridge arm of the power converter is obtained according to the predicted current and the actual current of each phase winding; finally, by comparing the actual switching state and the equivalent switching state, the decoupling fault diagnosis of the transistor of the power converter of the two-degree-of-freedom switched reluctance motor is realized.

2. The two-degree-of-freedom switched reluctance motor decoupling fault diagnosis method according to claim 1 comprises the following steps: Step 1: Calculate the predicted current value of each phase winding under different states at the (k+1)th sampling moment; Step 2: Obtain the actual switching state D of the switch tube of each phase bridge arm of the power converter according to the predicted current value of each phase winding, the reference current and the evaluation function; Step 3: Obtain the equivalent switch state D of each phase arm switch of the power converter according to the predicted current value and the actual current value of each phase winding at the (k+1)th sampling moment * ; Step 4: Compare the actual switching state D of each phase arm switch of the power converter with the equivalent switching state D * Perform fault diagnosis on power transistors of power converters; The specific operations of step 1 are: The predicted current value at the next moment is: Where k is the sampling point number; i(k) is the actual current value at the kth sampling moment; i(k+1) is the predicted current value at the (k+1)th sampling moment; ψ(k) is the flux linkage value at the kth sampling moment; U(k) is the phase voltage at the kth sampling moment; θ(k) is the rotor position angle at the kth sampling moment; ω(k) is the angular velocity at the kth sampling moment; R is the winding internal resistance; T s is the sampling period; The two-degree-of-freedom switched reluctance motor power converter adopts an asymmetric half-bridge structure. When the upper and lower power transistors are both turned on, an excitation circuit ST1 is formed. The predicted current is i up ; When the upper power transistor is turned off and the lower power transistor is turned on, the lower freewheeling loop ST2 is formed, and the predicted current is i free When the upper power transistor is turned on and the lower power transistor is turned off, the upper freewheeling loop ST3 is formed, and the predicted current is i free ; When both the upper and lower power transistors are turned off, a demagnetization circuit ST4 is formed, and the predicted current is i down ; The specific operations of step 2 are: The expression of the evaluation function is: J=[i ref -i pre (k+1)](2) In the formula, i ref is the reference current; i pre (k+1) is the predicted current value at the (k+1)th sampling moment; the actual switching state D of the bridge arm switch tube of each phase of the power converter is obtained according to the predicted current of each phase winding, the reference current and the evaluation function. The actual switching state D is 1, 0, -1 respectively, and the predicted phase current is i up 、i free 、i down ; The specific operations of step 3 are: When the actual current i(k+1) is equal to the predicted current i up When they are equal, the equivalent switch state D * is 1; when the actual current i(k+1) is equal to the predicted current i free When they are equal, the equivalent switch state D * is 0; when the actual current i(k+1) is equal to the predicted current i down When they are equal, the equivalent switch state D * is -1; The specific operations of step 4 are: When the actual switch state D is equal to the equivalent switch state D * If they are the same, the power transistor is in normal state; When the actual switch state D is 1, the equivalent switch state D * When it is 0, a shutdown pulse signal is injected into the upper power transistor; at the next sampling moment, when the actual current i(k+2) and the predicted current i free When the actual current i(k+2) is equal to the predicted current i down When they are equal, the lower power transistor has an open circuit fault; When the actual switch state D is -1, the equivalent switch state D * When it is 0, a conduction pulse signal is injected into the upper power transistor; at the next sampling moment, when the actual current i(k+2) and the predicted current i free When they are equal, the upper power transistor has a short circuit fault; When the actual current i(k+2) is equal to the predicted current i up When they are equal, the lower power transistor has a short circuit fault; When the actual switch state D is 0, the equivalent switch state D * When it is -1, the lower power transistor has an open circuit fault; when the actual switch state D is 0, the equivalent switch state D * When it is 1, the upper power transistor has a short circuit fault; When the actual switch state D is 1, the equivalent switch state D * When the actual switch state D is -1, the upper and lower power transistors both have open circuit faults; when the actual switch state D is -1, the equivalent switch state D * When it is 1, both the upper and lower power transistors have short circuit faults.

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